An electric arc furnace used for steel making typically consists of a refractory-lined vessel, covered with a retractable roof through which one or more graphite electrodes extend. The furnace includes an outer shell that consists of side walls and bottom in the shape of a “bowl.” Refractory materials line the bottom and side walls of the furnace. The inner surfaces of the side walls of the furnace are typically lined with continuous rings, i.e., continuous layers or courses, of refractory brick. The bricks in these continuous rings are tightly held in place as a result of each brick being constrained from movement by the adjacent bricks.
An electric arc furnace includes a slag discharge opening. This discharge opening is used to remove slag that typically forms along the upper surface of the molten metal within the electric arc furnace. The slag discharge opening is defined on the bottom by a sill formed by refractory bricks that are typically six (6) inches or less in height. The slag discharge opening creates a gap in the continuity of the courses of brick lining the inner surface of the side walls of the outer shell. In other words, a gap exists in the ring of bricks where the slag discharge opening is formed. Many steel makers simply stop laying the brick rings at the opening of the slag door. As will be appreciated, this configuration creates a structure wherein the bricks in the rings defining the slag opening are not constrained by adjacent bricks.
While the furnace can be operated with this type of construction, a problem exists following removal of slag through the slag discharge door. As slag is pulled or poured from the furnace through the slag opening, slag exiting the furnace flows over a sill area defined by the slag opening. Some residual slag may remain on the top of the sill where it can solidify, i.e., “build up,” and accumulate over time. This slag “build up” eventually constricts the opening of the slag door, making it necessary to periodically remove the solidified slag. Typically, this is done by a device that mechanically strikes or impacts the slag, forcing it back into the furnace. The hammering and impacting forces, necessary to remove the slag, also have a tendency to damage the refractories (bricks) forming the sill and the surrounding slag opening. Because the bricks above the sill that form the opening are not confined or locked into a complete ring, and because the bricks that form the sill are generally six (6) inches or less in height, it is not unusual for the impact forces to dislodge bricks from the sill, and from the areas above the sill, forcing them into the furnace. Such an occurrence makes it necessary to repair the sill and the area above the sill, which is an expensive and time-consuming undertaking that affects the operation of the electric arc furnace.
The present invention provides a sill and jamb assembly for forming a slag opening in an electric arc furnace that is less susceptible to damage and dislodgement during a slag removal process.